<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <input type="button" value="点击按钮修改div样式" id="bn">
    <div id="d"></div>
    <script>
     function my$(id) {
         return document.getElementById(id);
     }
    
    my$("bn").onclick = function (){
        var divStyleObjet =  my$("d").style;
        divStyleObjet.height = "200px";
        divStyleObjet.width = "300px";
        divStyleObjet.backgroundColor = "hotpink";
    }

    </script>
</body>
</html>